In general, intravenous therapy is used to administer substances directly into a vein of a patient. Many tubing systems used in administration of intravenous or parenteral therapy employ a drip chamber. The drip chamber prevents air from entering the blood stream, causing air embolism. The drip chamber also allows for a flow rate of the administered substance to be estimated. Further, the drip chamber offers a means to vent closed containers, such as bottles, thereby permitting filtered air to replace the fluid removed and thus avoiding the formation of a vacuum that would inhibit flow. Some substances that may be infused intravenously include volume expanders, blood-based products, blood substitutes, buffer solutions and medications.
Typically, the traditional IV infusion setup includes a pre-filled, sterile container (glass bottle, plastic bottle or plastic bag) of fluid(s) with a tubular port that allows the attachment of an IV set's drip chamber “spike”. The IV set's drip chamber includes: a drip chamber orifice that allows the fluid to form drops of an approximate volume at slow flow rates, making it easy to see the flow rate (and also to avoid the entrainment of air bubbles in the tubing); a long sterile tube with a variable restriction clamp to regulate or stop the flow of fluids; a connector to attach to the vascular access device (VAD); connectors and a one-way check valve to allow “piggybacking” (Secondary mode infusion setup) of another infusion set onto the same line, e.g., for adding a dose of antibiotics to a continuous fluid drip. Further, the addition of an infusion pump to the IV infusion setup allows for control over the flow rate and total fluid volume delivered to a patient.
In certain cases, where a change in flow rate and a total volume delivered would not have serious consequences, flow is produced by elevating the container above the patient and employing gravity pressure in concert with manual adjustment of a clamp and visual monitoring of the rate of drop formation in the drip chamber to regulate the flow rate. Limitations exist with regards the administration of multiple substances using such a gravity mode intravenous therapy setup.